The present disclosure relates generally to medical sensors and, more particularly, to sensors used for sensing physiological parameters of a patient.
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Many types of medical sensors, such as optical sensors, are used to measure physiological characteristics of a patient. Typically, an optical sensor provides emitted light, which is then scattered through a portion of a tissue of a patient and detected. Various characteristics of a patient can be determined from analyzing such light, such as oxygen saturation, pulse rate, tissue bilirubin, and so forth.
Pulse oximetry is typically used to measure various blood flow characteristics including, but not limited to, the blood-oxygen saturation of hemoglobin in arterial blood, the volume of individual blood pulsations supplying the tissue, and the rate of blood pulsations corresponding to each heartbeat of a patient. Measurement of these characteristics has been accomplished by use of a non-invasive sensor, which scatters light through a portion of the tissue of the patient where blood perfuses the tissue, and photoelectrically senses the absorption of light in such tissue. The amount of light absorbed and/or scattered is then used to calculate the amount of blood constituent being measured.
The light transmitted through the tissue is selected to be of one or more wavelengths that are absorbed by the blood in an amount representative of the amount of the blood constituent present in the blood. The amount of transmitted light scattered through and/or absorbed by the tissue will vary in accordance with the changing amount of blood constituent in the tissue. For measuring blood oxygen level, such sensors have typically been provided with a light source that is adapted to generate light of at least two different wavelengths, in accordance with known techniques for measuring blood oxygen saturation.
Known non-invasive sensors include devices that are secured to a portion of the body, such as a finger, an ear, or the scalp. In animals and humans, the tissue of these body portions is perfused with blood and the tissue surface is readily accessible to the sensor. More particularly, certain types of oximeter sensors are applied to a forehead of the patient. For example, an oximeter sensor attached to the inside of a stocking hat provides one technique for placing, retaining, and locating the sensor on a forehead of an infant. Such hats should fit securely on the head of the infant to help the sensor stay in contact with the tissue and apply an optimal pressure to the forehead. Indeed, measurement accuracy may diminish because of venous pulsations and/or less than optimal sensor contact caused by a loose hat or a hat that slips off the forehead.